Differential amplifiers exhibit internal effects, e.g., due to temperature variations or component value mismatches within manufacturing tolerances, that cause amplifier complementary output signals to be unbalanced in the sense of having significantly different direct current peak levels for corresponding excursions in the same direction. Similar effects may be produced, e.g., by temperature drifts in components in the amplifier input circuitry. These different levels are troublesome at least in differential signal operations because they cause the complementary signals to experience, during information state transistions, equal-amplitude crossings at different phases with respect to the time base of the binary digital signals depending upon temperature variations, signal strength, and internal gains of the amplifier. In the frequent cases where input information signal swings are in an amplitude range which is comparable to the magnitude of the imbalance between the complementary output signals those outputs may not cross at all during the transitions.
In a C. F. Wheatley U.S. Pat. No. 3,983,502 quiescent current flow in a differentially driven amplifier load is reduced by degeneratively feeding back to the input of the amplifier a low pass filtered version of the differential load signal. However, this approach would appear to compress amplifier low frequency gain as a function of that feedback rather than directly correcting the amplifier output imbalance as to noncoincident peaks of complementary signals.
A W. W. Brown et al. U.S. Pat. No. 4,027,152 merges differential amplifier outputs in a common peak detector, the output of which is used as an automatic gain control signal without affecting any possibile imbalance between the amplifier output signals.